The invention relates generally to rotating blades for use in turbomachines. More particularly, the invention relates to a rotating blades provided with part-span shrouds between adjacent blades.
The fluid flow path of a turbomachine such as a steam or gas turbine is generally formed by a stationary casing and a rotor. In this configuration, a number of stationary vanes are attached to the casing in a circumferential array, extending radially inward into the flow path. Similarly, a number of rotating blades are attached to the rotor in a circumferential array and extending radially outward into the flow path. The stationary vanes and rotating blades are arranged in alternating rows so that a row of vanes and the immediate downstream row of blades form a “stage”. The vanes serve to direct the flow path so that it enters the downstream row of blades at the correct angle. The airfoil portions of the blades or buckets extract energy from the working fluid, thereby developing the power necessary to drive the rotor and the load attached thereto.
The blades of the turbomachine may be subject to vibration and axial torsion as they rotate at high speeds. To address these issues, blades typically include part-span shrouds disposed on the airfoil portions at an intermediate radial distance between the outer tip and the root section of each blade. The part-span shrouds or shroud portions are typically affixed to each of the pressure (concave) and suction (convex) sides of each airfoil, such that the part-span shrouds on adjacent blades matingly engage and frictionally slide along one another during rotation of the rotor. Conventional part-span shrouds have substantial weight and typically require larger fillets at the shroud/airfoil interface to ease structural stress between the part-span shroud and the airfoil surface, and to support the part-span shroud on the airfoil. The weight and the required fillet design tends to result in less aerodynamic blades, and therefore, in a decrease in flow rate and overall performance of the turbomachine stage at issue.